Circuit breaker



May 28, 1945- T. LINDsTRoM ET A1. 2,401,005

C IRCUI T BREAKER Tur@ L {nds-from @www Patentedl May 2.8, 190467 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Application March 5, 1942, Serial No. 433,473 13 claims.` (c1. 20o-ss) This invention relates to circuit breakers and, more particularly, to circuit breakers of the type that are tripped instantaneously on overloads above a predetermined value and after a time delay on lesser overloads.

An object of the invention is the provision ofl a circuit breaker with an improved trip device comprising an electromagnet having an armature which is operable to effect tripping of the breaker and which is controlled by a current responsive bimetal element to provide inverse time delay operation on overloads up to a predetermined magnitude.

Another object of the invention is the provision of a circuit breaker With an improved trip device comprising anv electromagnet having an armature operable to effect tripping of the breaker, the armature being normally latched in unattracted position and released in response to the operation of a current responsive bimetal element.

Another object of the invention is the provision of a circuit breaker with an improved trip device comprising an electromagnet having two armatures one of which is operable to instantaneously effect tripping of the breaker upon the occurrence of overloads above a predetermined value and the other of which is controlled to provide inverse time delay tripping on overloads below the instantaneous tripping current.

Another object of the invention is the provision of a circuit breaker with an improved trip device comprising an electromagnet having two armatures one of which is operable to instantaneously eiect tripping of the breaker upon the occurrence of overloads in excess of a predetermined magnitude and the other of which is normally held latched in unattracted position and is released by the operation of a current responsive bimetal element to cause tripping of the breaker in response to overloads below said predetermined magnitude.

Another object of the invention is the provision of a circuit breaker as previously described wherein release of the inverse time delay armature is effected by the diiierential movement of a current responsive bimetal element and an ambient temperature compensating bimetal element.

Another object of the invention is to provide a circuit breaker having an improved trip mechanism comprising an electromagnet having two armatures or trip members which are operated at times simultaneously after a time delay to trip the breaker, and at other times, one of the trip members is operated instantaneously independently to trip the breaker.

Another object of the invention is to provide an improved circuit breaker in which a plurality of trip members are operated by a single electromagnet one of the trip members being normally latched against operation and being releasable after a time delay under certain conditions to effect tripping of the breaker.

Another object of the invention is to provide a circuit breaker having an improved trip mechv anism in which a plurality of trip members are provided, one trip member being operated at times independently of a second trip member, and at other times the one trip member is operated b-y the second trip member to trip the breaker.

-Another object of the invention is to provide a circuit breaker having an improved trip mechanism wherein a current responsive bimetal acting through an ambient` compensating bimetal operates a latch to release a trip member and cause tripping of the breaker.

Another object of the invention is to provide a circuit breaker with an improved trip device having an electromagnetic means which is operable to trip the breaker, a trip member operable by the electromagnet to trip the breaker, and normally latched member operable by the electromagnet when released to operate the trip member. A

Another object of the invention in accordance with a modication thereof is the provision of a circuit breaker having an improved trip device in which a pair of bimetal elements are normally latched one to the other to restrain operation of a trip member, one of the bimetals being heated in response to the current oi' the circuit and operable to unlatch the trip member to eiect tripping of the breaker under certain conditions, the other bimetal element being arranged to compensate the device for changes in ambient temperature.

Another object of the invention is the provision of a circuit breaker with an improved trip device which is simple, accurate and reliable in operation and inexpensive to manufacture.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation together with additional objects and advantages thereof will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings in which:

Figure l is a vertical sectional view through the center pole of a multiple circuit breaker embodying a trip device constructed in accordance with the invention;

Fig. 2 is an enlarged fragmentary sectional View of the trip device;

Fig. 3 is an enlarged fragmentary view, partly in section, showing a modified form of the trip device; and

Fig. 4 is an enlarged fragmentary view, partly in section, showing a further modification of the invention.

Referring to Figure 1 of the drawings, the circuit breaker is provided with an operating mechanism common to all of the poles which is mounted in a U-shaped main frame I1 having sides which are rigidly connected by a cross member I9. The frame I1 is mounted on the central portion of a base I`| of insulating material and is secured thereto by means of bolts 2| and 23. The outer ends of the sides of the frame are rigidly connected by a cross member 25.

The bolt 23 extends through the base and the cross member I9 and serves to rigidly secure a connector 21 of conducting material to the cross member and to the base I I. A shaft 29 extending through an opening in the connector 21 and through openings in the sides of the frame I1 pivotally supports a pair of arms 3| having their free ends integral with a contact arm 30 for the center pole. The contact arms 30 (Fig. l) for` the outer poles (not shown) are identical with the arm 30 for the center pole but are not provided with arms 3|. The contact arms for the outer poles are rigidly secured to a tie bar 61 which extends across all of the poles and which is clamped to the center pole contact arm 30 by means of a split clamp 1|) and a screw 1|. The three contact arms 30 are thus mechanically connected for movement together. Rectangular tubes 69 of insulating material between the tie bar 61 and contact arms 30 for the several poles serve to insulate the three movable contact arms and their associated contacts from the tie' bar 61.

The movable contact structures and the stationary contacts for the several poles are all alike and hence only the contacts for the center pole have been shown. The contact arm 30 pivotally carries a main movable contact member 41 and a movable arcing contact member 55. The main contact member 41 is pivoted on a pivot pin 49 supported in projections of the contact arm 30, and the movable arcing contact member 55 is pivoted on a pivot pin 51 supported in projections 59 of the arm 30. The main movable contact member 41 carries a contact 33, and a Contact 35 is secured to the arcing contact member 55. These contacts 33 and 35 are adapted to engage respectively fixed contacts 39 and 31 secured on a conductor 4|l which is in turn secured to the base II by means of bolts 43. The conductor 4| extends upwardly and is bent at right angles, the bent portion extending through an opening in the base II to form a terminal connector 45.

A spring 53 compressed between a spring seat on the contact arm 30 and a spring seat on the main contact member 41 provides contact pressure for the main contacts 33-39 when the contact arm is in the closed position. Contact pressure for the arcing contacts 35-31 is provided by a spring 33 surrounding a rod 5| pivotally connected to the arcing contact member 55 and slidable through an opening in a spring seat on the contact arm 39. The spring 63 is compressed between a washer 65, seated on a shoulder on the rod 6|, and the spring seat on the contact arm 30. The rod 6| has a nut 15 on the outer end thereof which acts to limit counterclocl-zwise rotation of the arcing contact member 55 about its pivot when the Contact arm 3D is moved to open the contacts. Counter-clockwise movement of the main contact member 41 is limited by a projection 13 thereon striking the body of the contact arm 3G. The adjustment of the nut 15 on the rod 6| is such that the arcing contacts 35-31 open after the main contacts 33-39 open during an opening operation of the circuit breaker7 and close before the main contacts close during a closing operation.

When the contact arm 30 is operated to open the contacts, the arc across the arcing contacts 35-31 resulting from the rupture of the current is drawn into an arc extinguisher indicated generally at 16 where it is cooled and extinguished. Any suitable arc extinguisher may be employed, the one illustrated comprising, generally, a stack of slotted plates (not shown) of magnetic material disposed adjacent the paths of travel of each of the arcing contacts 35. The plates serve to draw the arc towards the ends of the slots where it is broken up into a plurality of short arcs which are quickly cooled and extinguished.

The movable arcing contact member 55 is connected by a flexible shunt conductor 11 to the main contact member 41 and another flexible shunt conductor 19 connects the main contact member 41 to the connector 21. The connector 21 for the center pole is secured to the cross member I9 of the frame I1 by the bolts 23, and the connectors 21 for the outer poles are bolted to the base II with a spacer (not shown) between the base and each of these connectors in order to align the members 21 of the outer poles with the corresponding member 21 for the center pole. A conductor 8|, secured to the connector 21 by means of bolts 14 extends downwardly therefrom and is electrically connected to a terminal connector 83 which, together with the terminal connector 45, serves to connect the breaker in an electrical circuit.

The electrical circuits for each oi the several poles of the breaker are essentially the same. The circuit for the center pole extends from the terminal connector 45 through the conductor 4I, the main contacts 33H39, the main contact member 41, the flexible shunt conductor 19, the connector 21, the conductor 8| to the terminal connector B3. The circuit for the arcing contacts 31-35 extends from the terminal connector 45, through the conductor 4|, the arcing contacts 31-35, contact member 55, the flexible shunt conductor 11, the main contact members 41, and through the previously described circuit to the terminal connector 83.

The contact arms Si) are biased in a clockwise or opening direction by means of a pair of springs 85 (only one being shown). These springs are tensioned between the center pole contact arm 3i) and a xed pivot 81 supported in the main frame I1. In the closed position of the breaker, the center pole contact arm 30 and consequently all of the contact arms are releasably restrained in closed contact position (Fig. 1) by means of a toggle and linkage mechanism which is collapsible to cause opening of the contacts. The toggleand linkage forms a part of the common operating mechanism.

This collapsible linkage includes a lever 89 pivotally mounted on a fixed pivot 9| supported on the main frame I1. The lever 89 comprises a pair of levers rigidly connected by an integral cross bar l I1, and is operatively connected to the support arms 3| of the center pole contact arm 30 by a main operating toggle comprising toggle links 93 and 95. The toggle link 93 has one end pivoted. on a pin supported on the lever 89 and the link 95 is pivoted on a pivot pin 99 on the arms 3|. The links 93 and 95 are pivotally connected by a knee pivot pin 91. The toggle link 95 comprises a pair of links rigidly connected by means of an integral cross bar I5.

The free end of the lever 89 is pivotally connected by means of a link |03 to one arm of a lever pivoted on the xed pivot 81. The other arm of the lever |05 is pivotally connected to a toggle link |01 of a tripping toggle comprising the link |01 and a toggle link |09. The link |09 is pivoted on a iixed pivot H3 supported on the frame I1 and comprises a pair of links joined near the pivot H3 by an integral yoke |23 provided with projections |25 and |21. The toggle link |01 comprises a pair of links connected by an integral yoke H9 having a bent portion to which is secured an extension |2| of insulating material. The toggle links |01 and |09 are pivotally connected by a knee pivot pin ||I. The purpose of the extension I2 I is to cooperate with a part connected to a manually operable handle |4| to manually trip the breaker in a manner to be more fully described later. The lever |05 and the link |03 each comprise a pair of members rigidly connected by yokes substantially as illustrated.

The linkage just described serves to releasably hold the contact assemblage including the movable contacts ior all oi the poles of the breaker in closed contact position. In the closed position, the main operating toggle 93-95 is overcenter above a line through the center of the pins 99|0|, and a second toggle, one link of which comprises the overcenter links 93-95 and the other link of which comprises the lever 89, is overcenter above a line through the center of the pins 99 and 5|. The overcenter movement of the main operating toggle 93--95 is limited by the projecting end of the link 93 engaging the cross bar H5 of the link 95.

With the main operating toggle 93-95 and the toggle comprising the links 93-95 and the lever 89 in the overcenter position, as shown in Fig. l, the springs 85 bias the lever 89 in a clockwise direction. Clockwise movement of the lever 89, however, is normaily prevented by the tripping toggle |01--I09 which is overcenter to the left of a line through the center of the fixed pivot H3 and the point of connection of the toggle link |91 with the lever |05. The toggle |01|09 is biased to its overcenter position by a spring |28 tensioned between the yoke H9 and the fixed pivot H3. The overcenter position of the tripping toggle |01-I09 is adjustably determined by the projection |25 of the yoke |23 engaging an adjusting screw |29 in the cross memf` ber 25 of the frame. The tripping toggle |01- |09 in its overcenter position, acting through the lever |05and the link |03, prevents clockwise movement of the lever 89 and consequently holds the movable contact assemblage in the closed contactposition against the biasing influence of the springs 85.

The tripping toggle Inl- |09 is adapted to be moved overcenter outwardly in a direction to cause its collapse to effect opening of the'contacts by means of a trip device indicated generally at |33 (Fig. 1). The trip device is operable in response to overload currents in the circuits of the breaker to actuate a trip rod |35 and cause collapse of the tripping toggle |01- 109. The trip rod |35 is slidable vertically lthrough a shunt trip coil (not shown) enclosed vin a casing |98 attached to the main frame I1. The shunt trip coil forms an additional tripping means for tripping the breaker. The shunt coil is adapted to be energized from a suitable source and in a manner well known in the art, to operate the trip rod and trip the breaker from a remote point.

When operated either by the shunt coil or by the overload trip device |33, the trip rod |35 is thrust upwardly and strikes the projection |21 of the yoke |23 and rocks the toggle link |09 clockwise about the fixed pivot I I3. This movenient of the link |09 causes collapse of the tripping toggle H11-|99 permitting clockwise movement of the lever 89 which permits the springs to rock the movable contact assemblage clockwise to open the contacts.

The main operating toggle 93-95 does not immediately collapse but the force of the springs 95 applied through the contact arm 30--3I and the main operating toggle causes collapse of the toggle comprising the links 93-95 and the lever 99 which results in a clockwise movement of the lever 89. This movement is transmitted through the link |03 and the lever |55 to complete the collapse of the tripping toggle |01--I09.

The clockwise or opening movement of the contact arm 30 is arrested by projections (not shown) thereon striking portions |31 of the frame |1. At this time the rebound of the inertia of the main operating toggle 93-95 and the parts of the linkage 89, |03, and |05 starts the main operating toggle 93-95 overcenter in a direction to cause its collapse. By the time the knee pin 95 of the toggle has passed overcenter below the line 99|0| the weight of the parts act to complete the collapse of the toggle 93-95 and causes the linkage 80, |93, |05 and the tripping toggle |01|09 to be automatically reset to their normal position. The main operating toggle 93-95 remains in collapsed condition until the contacts are closed.

The contacts are closed manually by operation of the previously mentioned handle |l||. The handle is rotatably mounted in a bracket |43 of insulating material secured to the outer end of the main frame |1. Operatively connected to the mechanism (not shown) operated by the handle is a link |5|. The lower end of the link |5| is recessed and straddles a pulleyshaped projection |53 rigidly secured on a cross member |41 rigidly connecting the outer ends of a pair of spaced contact closing levers |45. These levers are disposed on the outside of the frame I1 and are pivotally supported on the ends of the fixed pivot 9| which project beyond the sides of the frame |1. The inner ends of the levers l|45 are rigidly connected by a cross member I49. Spaced projections |52 extending from the center portion of the cross member |49 support a pivot pin |51 upon which is r0- tatably mounted a roller |55.

The contacts are closed manually by clockwise rotation of the handle |4|. This movement of the handle, through connections (not shown) thrusts the link downwardly and due to its engagement with the projection |53, rotates the closing levei` |45 in a clockwise direction. During this movement of the lever |45, the roller |55 engages the link 93 of the now collapsed main operating toggle 93-95 and moves this toggle to its overcenter position. Since at this time the tripping toggle |01-|09 has been restored to its overcenter holding position, rotation of the lever 89 is prevented and consequently the force applied by the roller |55 to straighten the toggle 93--95 rotates the Contact arm 30 counterclockwise to close the contacts and to tension the springs B5. The clockwise movement of the closing lever |45 lmoves the toggle 93-95 overcenter above the line 99|0| so that the contacts are held in the closed position until the breaker is again tripped.

Upon release of the handle |4| following a contact closing operation, a spring |59 tensioned between the closing lever |45 and the frame |1 restores the lever |45 in a counterclockwise direction. This movement of the lever |45 and the projection |53 thrusts the link |5| upwardly to restore the handle |4| to its neutral position.

The closing lever |45 may be operated to automatically close the contacts through the agency of a motor |39 (Fig. l) mounted on a plate at tached to the side of the frame I1. The motor |39 may be energized from any suitable source. When energized, the motor is adapted, through a suitable driving connection, to rotate a crank disc |30. This disc carries an anti-friction roller |3| which is adapted to engage a cam face |32 on an arm |34 secured to one side of the closing lever |45 and rotate the arm and the closing lever |45 clockwise to effect closing of the contacts in the ,previously described manner. As soon as the roller |3| passes out of engagement with the arm |34, the spring |59 acts to restore the lever |45 to its normal position. The motor |39 is deenergized by a suitable limit switch (not shown).

The circuit breaker may be tripped manually by rotation of the handle |4| through a small angle in a counterclockwise direction from its neutral position, When the handle is rotated in tripping direction, a projection (not shown) on the link |5| engages the extension |2| on the yoke ||9 oi the toggle link |01 and rocks the link counterclockwise about its point of connection with the lever |051. This moves the tripping toggle |01|09 overcenter in a direction to cause its collapse and eiects opening of the contacts in the previously described manner.

As previously stated, the trip rod |35 is operated to effect tripping of the breaker by means of a current responsive trip device |33. There is a trip device |33 provided for each of at least two of the poles of the breaker but since the trip devices are alike only the one for the center pole is shown and will be described.

Referring to Fig. 2, the trip device includes an electromagnet indicated generally at |60 includ ing a magnet core |61 having upwardly extending end pieces |53 l(only one being shown) secured thereto, both the core |6| and the end pieces |63 being constructed of magnetic material. The end pieces |03 are securely mounted on a U-shaped frame |55 of non-magnetic material comprising parallel side members |61. A spacer |69 is secured to the frame |55 by means of screws |1| (only one being shown), and the frame and the spacer are secured to the base by bolts |13 (only one being shown). The outer ends of the side members |01 are rigidly connected by a cross member |15 formed integral therewith. An energizing coil 82 electrically connected to, or formed integral with, the conductor 8|, makes one Complete turn about the core |6| and forms the energizing winding for the magnet structure |50. The other end of the conductor 0| is electrically connected to the terminal 83. A trip lever |11 comprising a pair of parallel levers of non-magnetic material is pivotally supported on the frame |55 Vby a pivot pin |19. The levers |11 are rigidly connected at their outer ends by means of a yoke |8| and are joined at their opposite ends by a relatively small armature |83. The trip lever |11 is biased against operation by the magnet |60, by means of a pair of springs |9| (only one being shown) having one end hooked to the yoke |8| and the other end anchored to a vertically movable plate |93. The plate |93 cooperates with an adjusting screw |95 which is provided with a knurled head |91 bearing against the bottom side of the cross member |15. Rotation of the screw |95 moves the plate |93 and thereby adjusts the tension of the springs |9| to vary the minimum overload tripping point of the breaker. A scale plate 203 supported on the outer ends of the cross member |15, bears indicia which indicates the trip setting of the breaker.

A trip bar |81 is rotatably supported in a bracket |89 secured to the casing |30 (Fig. l) for the shunt trip coil. The trip bar |31 extends across all the poles of the breaker and is provided with an arm |05 for each pole (only one being shown), the center one or" the arms being in alignment with the lower end of the trip rod |35. An adjusting screw |99 is mounted in each of the yokes |8| in alignment with the correspending arm and is locked in adjusted position by means of a lock nut 20|.

Normal rated current owing through the circuit of the breaker, including the energizing winding 82, causes slight energization of the magnet |50, but not suilicient to overcome the tension of the spring |9I. Upon the occurrence of an overload current above a predetermined value, for example, above l() to l2 times rated current in the circuit of any pole, the flow of current through the corresponding coil 82 causes ener gization of the magnet |50 sufficient to overcome the tension of the springs |9| and attract the armature |33 rocking the trip lever |11 counterclockwise. At this movement of the trip lever |11, the screw |99 engages the corresponding arm |05 of the trip bar and rocks the trip bar |81 in a clockwise direction thereby thrusting the trip rod |35 upwardly to trip the breaker in the previously described manner.

Means are also provided to effect tripping of the breaker after a time delay in response to persistent overload currents below the predetermined value. This means includes a trip lever 205 comprising a pair of parallel levers of nonmagnetic material pivotally mounted on the pivot |19 and disposed between the sides of the previously described lever |11. The trip levers 205 are rigidly connected at their outer ends by means of a cross bar 201, and a relatively large arma.-

ture 209 is secured to their opposite ends in juxtaposition with the end pieces |63 oi the magnet core. The trip lever 205 is normally latched against operation by the magnet |60, by a latch member 2| l which normally engages the cross bar 201. The latch member 2|| is secured to a pivot rod 2|3 by a set-screw 2|5, and the rod 263 is pivotally supported by projections 2|1 (only one being shown) formed integral with the frame IE5 and extending upwardly from the cross mem-- ber |15.

An ambient compensating bimetal element 2 9, secured to the latch member 2|| by means of rivets 22|, extends substantially horizontally from the latch member toward the base i. A low temperature thermally responsive bimetal element 223 is supported by a metal bracket 225 to which it is rigidly secured by welding or in any suitable manner. The low temperature responsive bimetal may comprise any bimetal element in which one side has a relatively high coefficient of expansion and the other side has a relatively low coeicient of expansion and which will deflect in response to a relatively small change in tem perature. The bracket 225 is secured by means of screws 221 to the conductor 8| at the left of the coil 82 of the magnet, the bimetal element 223 extending outwardly and toward the right above the coil and having its free end disposed just below the free end of the compensating bimetal 2|9. The free end of the bimetal 223 has a nut 229 rigidly secured thereto in which is threaded an adjusting screw 23| of insulating material. The screw 23| has an enlarged lower end 233 also of insulating material formed integral therewith, the purpose of which will be described later.

The bimetal element 2|9 is disposed to deflect upwardly in response to an increase in ambient temperature, and the bimetal element 223 is disposed to deflect upwardly in response to an increase in ambient temperature or in temperature generated by an overload current flowing through the conductor 8| and the coil 82, When the bimetal element 223 deects upwardly a predetermined amount in response to an increase in temperature of the conductor 3| resulting from the flow of overload current, the screw 23| engages the free end of the compensating bimetal 2I9 and rotates the latter and the latch member 2| clockwise to disengage the latch member from the cross bar 251. The increased energization of the magnet |60 occasioned by the overload current is sufficient to attract, the large armature 299 and rotate the trip lever 205 counterclockwise, As previously stated, overload currents below a predetermined value do not energize the magnet |50 sufficiently to overcome the tension of the springs |9| and operate the trip lever |11 due to the smaller size of the armature |83. The larger armature 209, however, provides for an increased flow of magnetic llux and, therefore, a greater magnetic pull so that when the latch member is operated to release the trip lever 205, the magnet immediately attracts the armature and rotates the trip lever 205 counterclockwise. Due to the engagement of the trip lever 205 with the armature |83, this movement of the trip lever 205 rotates the trip lever |11 therewith to effect tripping of the breaker, as previously described. e

When the circuit is interrupted at the main contacts (Fig. l), the magnet |60 is deenergized and the springs |9| (Fig. 2) restore the trip lever |11 to normal position and, by means of the armature |83, restore the trip lever 2705 to its normal position. As the bimetal element 223 cools and resumes its normal position, it permits the bimetal element 2|9 to rotate counterclockwise, thus restoring the latch member to latching engagement with the cross bar 201. The clockwise or restoring movement of the trip lever 205 is limited by an adjusting screw 235 which is locked in position by a lock nut 231. Due to the engagement of the lever 205 with the armature |83, the screw 235 also limits the clockwise movement of the trip lever |11.

The previously mentioned, enlarged end 233 of the screw 23| forms a part of a device for varying the amount of time delay provided by the bimetal element 223, that is, the amount of deflection of the bimetal that is required to release the latch. This result is obtained by rotating the insulating screw 23| to thereby adjust the distance of the end of the screw from the bimetal 2|9.

The squared upper end 239 of an adjusting member 24| of insulating material ts relatively loosely within serrations formed on the inside of the enlarged end 233 of the screw 23| forming a slidable connection between the member 24| and the screw 23|. The member 24| is provided with a portion 243 substantially spherical in shape which is supported for universal movement in a U-shaped convex metal band 225 passing around the portion 243 and having its ends secured by means of screws 246 (only one being shown) to a bracket 241 which, in turn, is securedby means of a screw 249 to the underside of the frame |55. The lower end of the member 24| is formed in the shape of a knurled head 25| and is provided with a lug 253 which is adapted to engage a projection 255 of the bracket 241 to limit the rotation of the member 24|.

The end 251 of the bimetal 223 which projects to the right of the nut 229 is bent downwardly and is tensioned against the periphery of 233 which is provided with a plurality of flat surfaces in order to retain the screw member 233 and the screw 23| in adjusted position.

Since the end 233 of the screw 23|y is movable axially relative to the member 24|, rotation of this member does not move the bimetal 223 but merely moves the end of the screw 23| toward and away from the bimetal 2|9 and in this manner varies the time delay provided by the bimetal element 223.

When the bimetal 223 deilects upwardly in response to overload currents, it moves the axis of the screw 23| and the enlarged end 233 thereof upwardly and slightly in a counterclockwise direction out of the normal position, moving the member- 233 slightly toward the right. This movement, through the slidable connection 233-239, rotates the adjusting member 24| slightly clockwise, the spherical portion acting as the pivot. Since the member 24| is freely movable in its support bracket or band 245, it imposes no restraint on the deecting movement of the bimetal 223.

The enlarged end portion 233 with its serrated inner surface, and the square portion 239 of the member 24| also serve as a means for calibrating the bimetal element to correspond to the trip setting of the adjusting screw |95. When the minimum trip setting of the device is adjusted by the screw |95, it is necessary to recalibrate the bimetal 223 accordingly and this is done by removing the adjusting member 24| and turning the screw 23|l to obtain the proper distance of the screw end from the free end of the bimetal 219 corresponding to the new trip setting of the screw |95, and then reassembling the member 24|.

Since the bimetal element 223 is a low tem* perature blmetal, that is, one which will deflect when its temperature is increased a relatively small amount, it can be heated by conduction directly from the conductor 82 without any resistance heating means and without any current ow through the blmetal. By this construction overload currents cannot damage the bimetal element or alter its calibration, and there is no heater which might be burned up as in the case of some prior art devices.

The blmetal elements 2|9 and 223 have the same characteristics and deect upwardly the same extent in response to an increase in ambient temperature. It can be seen, therefore, that the additional deflection of the bimetal 223, in order to trip the breaker in response to an overload of given magnitude and duration, will remain the same for any ambient temperature within the limits of the device.

Fig. 3 illustrates a modifi-cation of the invention in which an ambient compensating bimetal carried by a trip member is latehed directly to a thermally responsive blmetal element to control tripping of the breaker on overloads below the predetermined value. In the modification shown in Figs. 3 and 4, like parts have been given the same reference characters. This trip device includes a U-shaped magnet core 25 and a frame 283 of non-magnetic material comprising parallel side members 295 rigidly connected by a crossI member 261. Each of the side members 285 is provided with an angularly bent foot 269 abutting against the magnet core 26|, and the frame and the magnet core are secured to the base by means of bolts 21| (only one being shown). A trip lever comprising a pair of arms 213 is pivotally mounted on a rod 215 supported in the frame 263. At their inner ends the arms carry an armature 211 and the outer ends of the arms 213 are rigidly connected by a. yoke 219. The trip lever 213 is biased against operation by the magnet 26|, by means of a pair of springs |9| having one end secured to the yoke 219 and the other end attached to the vertically movable plate |93. A conductor 28| secured to the connector 21 (Fig. 1) in place of the conductor 8| and coil 92 of the previously described trip device, extends downwardly and between the legs of the magnet core and thereby forms a single turn energizing coil for the magnet core. The end of the con-- ductor 28| extends substantially horizontally through an opening in the base and forms a terminal connector 283.

The conductor 28| serves to energize the magnet 26|; however, on low overloads below a predetermined value, this energization is insufficient to overcome the tension of the springs |9| and effect tripping of the breaker. On overloads above a predetermined value, for example above l0 `to 12 times rated current, the pull of the magnet 1s sufcient to overcome the springs |9|, attract the armature 211, and operate the trip lever 213 to trip the breaker in the previously described manner.

The current responsive inverse time limit tripping means of the Fig. 3 modification includes a trip lever 285 of non-magnetic material comprising a pair of spaced arms pivotally mounted on the rod 215 and connected at their outer ends by means of a yoke 281. A relatively large armature 289 is secured to the inner ends of the arms of the lever 285 for cooperating with the magnet 26 I. A low temperature thermally responsive bimetal element 29|, secured to the underside of the conductor 28| by means of two rivets 293 (only one being shown), has a latch member 295 secured to but insulated from its free end. An ambient compensating bimetal element 291 has one end rigidly secured to a iiattened portion o.' a shaft 299 rotatably supported in the ends oi the lever arms 235. A latch member 39| secured to but insulated from the free end ol the ambient blmetal 291 cooperates with the latch member 295 to normally prevent operation oi the trip lever 285 by the magnet 29|. An adjusting screw 393 is threaded into an opening in the shalt 293 in alignment with one of the arms or the levell 213 and is locked in adjusted position by a lock nut 395. Another adjusting screw 3D1 in the cross member 251 of the frame 295 forms an ad justable stop for the trip lever 295 and is engageable by the yoke 281 of the lever. A lock nut 339 maintains the screw in adjusted position. The springs |9| bias the trip lever 223 in a clockwise direction against the screw 393 and by means of the screw and the shaft 299 biases the trip lever 285 also clockwise into contact with the screw 391. The screw 303 serves as an adjustable stop between the trip levers 285 and 213. The screw 381 serves as an adjustment to obtain proper clearance at the latch point. This screw 391 should preferably be adjusted for a maximum clearance of .005 of an inch at the latch point.

An adjustment is provided to adjust the overlap of the latch members 295 and 38|. This adjustment includes a resilient spring strip 3H secured to the compensating blmetal element 291 at the point where the bimetal is secured to the shaft 299. The member 3|| has a substantially horizontal portion adjacent the blmetal 291 and is bent downwardly as at 3|3 to the right thereof and engages the right-hand end oi an extension 3 I4 of the yoke 281. To the left of the shalt 299, the member 3|| inclnes downwardly and. at a point near its left-hand end, engages an adjusting screw 3|5. The screw 3|5 is held in position in the yoke 281 by a lock nut 3|1.

The member 3|| is tensioned between the end of the screw SI5 and the end or the extension 3M. Rotation ol the screw 3|5 in a direction to move it upwardly increases the tension of the member 3|| and causes a slight clockwise rotation of the shalt 299 and the blmetal 291 to increase the latch overlap. Movement of the screw 3|5 in the opposite direction decreases the tension of the member 3| and effects a reduction in the latch overlap. The tension of the spring |94 is adjusted in the previously described manner and for the same purpose.

Upon the occurrence of an overload below the predetermined value, the pull of the magnet 26| increases, and the blmetal 29|, when heated a predetermined amount deilects upwardly to disengage the latch member 295 'from the latch 39|. When this occurs, the magnet 23| attracts the large armature 289 and rocks the trip lever 285 counterclockwise, which movement through the agency of the shaft 299 and the screw 383, rocks the trip lever 213 in the same direction to effect tripping of the breaker in the manner previously described.

When the current is interrupted and the magnet 26| is deenergized, the spring |9| restores the trip lever 213 to its normal unattracted position as shown, and by means of the connection 299-383 restores the lever 285 to the position shown. As the blmetal 29| cools and resumes its normal position, the latch 295 reengages the latch 30|.

The bimetal elements 29| and 291 have the same characteristic and deflect upwardly an equal extent in response to a rise in ambient temperature, thus providing a maximum correction for variations in ambient temperatures.

According to the modication shown in Fig. 4 of the drawings, the breaker is tripped after a time delay in response to overloads below the predetermined value under the control of an oil dashpot. On overload currents above the predetermined value, the breaker is tripped instantaneously independently of the dashpot.

The trip lever |11 shown in Fig. 4 is identical with the lever |11 shown in Fig. 2 and operates in the same manner to trip the breaker instantaneously on overloads above the predetermined value. The magnet |60, including the magnet core |6||63 and the energizing coil E2, is the same as that shown in Fig. 2, and the trip lever 205 is the same as the one shown in Fig. 2 with the exception that the cross bar 201 is omitted, the right-hand arms are shortened and are operatively connected by means of a rod 3l!) and pivot pin 32| to the piston 323 of a dashpot indicated generally at 325. The dashpot 325 may be of any suitable type, such, for instance, as is fully disclosed in the copending application of John W. May and William H. Stuellein, Serial No. 392,048, tiled May 6, 1941, and assigned to the assignee of the instant invention, which application became Patent No. 2,340,973 on February 8, 1944. The dashpot is of the suction disk type and comprises a cup-shaped member or pot 321 secured to 4the bottom of the frame |65 and at least partially filled with oil. The piston 323 is provided with suction surfaces (not shown) on its lower face which cooperate with similar suction surfaces (also not shown) in the bottom of the cup 321. The cup is so mounted that it may be rotated to vary the eiiective suction area which provides a convenient means of determining the tripping time delay of the breaker on overloads below the predetermined value.

As previously mentioned, the magnet |60 is energized sufficiently to instantaneously trip the breaker when an overload above the predetermined Value or a short circuit occurs, the trip lever |11 operating independently of the trip lever 205 and the dashpot.

Normal rated current flowing through the coil 82 does not energize the magnet |50 suiciently to attract the armatures |83 and 209 and overcome the tension or the spring |91. When an overload current below the predetermined value occurs, theincreased energization of the magnet |60 creates a pull on the armatures sumcient t overcome the spring |91 and applies a force on the rod 3|9 in an upward direction, which, after a time delay determined by the magnitude and duration of the overload, breaks the suction or oil seal between the suction surfaces of the piston 323 and the cup 321. The magnet |60 then attracts the armatures and aperates the trip levers |11 and 2&5 to trip the breaker. When the overload current is interrupted, the springs |9| function to restore the lever |11, and by means of the armature |83, the lever 205 to normal position as shown in Fig. 4.

We claim as our invention:

l. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip mechanism comprising a trip member operable to cause opening of the contacts, an electromagnet operable in response to overload currents above a predetermined value to instantaneously operate the trip member, a second member operable by said magnet to operate the trip member, a latch normally restraining said second member against operation and operable to release said second member, a thermally responsive bimetallic element heated in response to the current of the circuit and operable when heated a predetermined amount in response to overload currents belovi7 said predetermined value for operating said latch, and an ambient responsive bimetallic element intermediate the thermally responsive bimetallic element and the latch for compensating the device for changes in ambient temperature.

2. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of said contacts, an electromagnet operable in response to overload currents above a predetermined value to operate said trip member, a second member operable to operate the trip member, a latch normally restraining said member against operation and operable to release said member, an ambient temperature responsive bimetallic element secured to said latch, and a thermally responsive bimetallic element heated in response to the current of the circuit and operable when heated a predetermined amount to engage said ambient temperature responsive bimetallic element and operate `the latch, said ambient temperature responsive bimetal compensating the device for changes in ambient temperature. K

3. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of the contacts, an electromagnet operable in response to overload circuits for operating said trip member, an armature operable by said electromagnet under certain conditions t0 operate the trip member, said trip member being operable under certain other conditions independently of said armature, a latch member normally latching said armaturel against operation and movable to an unlatching position to release the armature, an ambient temperature responsive bimetallic element operatively associated with said latch member, and a thermally responsive birnetallic element heated in response to the current of the circuit and operable when heated a predetermined amount to cause said armature to be released, said ambient responsive bimetallic element acting in response to changes in ambient temperature to compensate the device for changes in ambient temperature.

4. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of the contacts, an electromagnet operable in response to overload currents above a predetermined magnitude to instantaneously operate said trip member, a second member operable by said electromagnet in response to overload currents below said predetermined magnitude to operate said trip member, said trip member being operable instantaneoush7 upon overloads above said predetermined magnitude independently of said second member, an ambient responsive bimetallic element operatively associated with said second member, and a thermally responsive bimetallic element cooperating with said ambie-nt responsive bimetallic element to normally restrain the member against operation, said thermally responsive bimetallic element being heated in response to the current of the circuit and operable when heated a predetermined amount by overload currents to release said second member and permit said second membcr to operate the trip member'.

5. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including an electromagnet, a trip member operable by said electromagnet under certain circuit conditions to cause instantaneous opening of the contacts, an auxiliary member operable by said electromagnet under certain other circuit conditions to operate the trip member, an ambient temperature compensating bimetal element operatively associated with said auxiliary member, and a thermally responsive bimetal element cooperating with said ambient compensating bimetal element to normally restrain the auxiliary member against operation, said thermally responsive bimetal element being operable when heated a predetermined `amount in response to said certain other circuit conditions to release the auxiliary member and thereby cause the electromagnet to operate the trip member.

6. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of said contacts, an electromagnet operable in response to overload currents above a. predetermined value to instantaneously operate the trip member, an auxiliary member operable by said magnet to operate the trip member, a latch member normally restraining said auxiliary member against operation, a pair of bimetallic elements disposed to deiiect in the same direction when heated, one of said bimetallic elements being operatively associated with the latch member and responsive to changes in ambient temperature, and the other of said bimetallic elements being heated in response to the current f the circuit and operable when heated a predetermined amount in response to overload currents below the predetermined amount to effect unlatching of the auxiliary member.

7. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of said contacts, an electromagnet operable in response to overload ourrents above a predetermined value to instantaneously operate said trip member, an auxiliary member operable by said electromagnet to operate the trip member, a latch member for restraining said auxiliary member against operation, a pair of bimetallic elements disposed to deflect in the same direction when heated, one of said bimetallic elements being operatively associated with said latch member, and the other of said bimetallic elements being operable when heated a predetermined amount in response to overload currents below said predetermined value to cause operation 0f the latch member to release said auxiliary member, and adjusting means comprising an adjustable member rotatably mounted on the thermally responsive bimetallic element and movable therewith and a member mounted for universal movement in a xed support for operating said adjustable member to determine the unlatching point of the latch member.

8. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts. a trip device including a trip member operable to cause opening of said contacts, a latch normally restraining said trip member against operation and operable to release said member, an ambient temperature responsive bimetallic element secured to said latch, and a thermally responsive bimetailic element heated in response to current of the circuit and operable when heated a predetermined amount to engage the ambient temperature responsive bimetallic element and operate the latch, said ambient temperature responsive bimetallic element compensating the de'- vice for changes in ambient temperature.

9. A circuit breaker comprising relatively movable contacts, operating mechanism therefor, a trip device including a trip member operable to cause opening of the contacts, a latch normally restraining said trip member against operation and operable to release said trip member, an ambient temperature responsive bimetallic element secured to said latch, a low temperature rcsponsive bimetallic element disposed in heat conducting relationship to a current conductor of the breaker and operable when heated a predetermined amount to engage the ambient temperature responsive bimetallic element and operate the latch, said ambient temperature responsive bimetallic element compensating the device ior changes in ambient temperature.

10, A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of said contacts, a latch member for restraining said trip member against operation, a pair of bimetallic elements disposed to deflect in the same direction when heated, one of said bimetallic elements being operatively associated with the latch member, and the other of said bimetallic elements being operable when heated in response to overload currents to cause operation of the latch member to release the trip member, an electromagnet operable in responso to overload currents to operate said trip member, and adjusting means comprising an adjustable member rotatably mounted on the thermally responsive bimetallic element and movable therewith and a member mounted for universal movement in a fixed support for operating said adjustable member.

1l. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including a trip member operable to cause opening of the contacts, an electromagnet operable in response to overload current above a predetermined value to operate the trip member, a second member operable to operate the trip member, a latch member for normall-y restraining said second member against operation, said latch member lbeing pivoted on a fixed pivot, an ambient temperature responsive bimetal element secured to said latch member, and a thermally responsive bimetal element heated in response to the current of the circuit and operable when heated a predetermined amount to move the ambient 'temperature responsive bimetal and operate the latch, said ambient temperature responsive bimetal compensating the trip device for changes in ambient temperature.

12. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including an electromagnet, a trip member operable by said electromagnet in response to overload currents above a predetermined value to cause instantaneous opening of the contacts, an auxiliary member operable by said electromagnet to operate the trip member, an ambient temperature responsive bimetal element mounted on said auxiliary mem-- ber for movement therewith, a thermally responsive bimetal element cooperating with said ambient temperature responsive bmetal to normally restrain said auxiliary member against operation, said thermally responsive bimetal element being operable when heated a predetermined amount in response to overload currents to release the auxiliary member and thereby cause the electromagnet to operate the trip member.

13. A circuit breaker comprising relatively movable contacts, operating mechanism therefor, a trip device including a trip member operable to cause opening of the contacts, an eleotromagnet operable in response to overload currents above a predetermined value to instantaneously operate said trip member, an auxiliary member operable by said electromagnet to operate the trip member, an ambient temperature responsive bimetal element mounted on and movable with said auxiliary member, a latch member on said bimetal element, a thermally responsive bimetal element, a latch on said thermally responsive bimetal element cooperating with said latch member to normally restrain the auxiliary member against operation, said thermally responsive bimetal deecting when heated a predetermined amount in response to overload currents below said predetermined value to release said auxiliary member and thereby cause the magnet to operate the trip member.

TURE LINDSTROM.

JOHN W. MAY. 

